10
Final air/oil separation is obtained using a
composition material “can” type separator
element to provide nearly oil free air at the
separator out or service connection. Oil
collected by the separator element is
returned to the system by a filter equipped
separator drain line.
To prevent over pressuring the air received/oil
reservoir, an air pressure relief valve is
installed in the received/reservoir. This
pressure relief valve is located on the
upstream or wet side of the separator
element.
Oil flows, forced by air pressure, from the air
receiver/oil reservoir through the cooler and
filter and its injected into the air end to
provide cooling, sealing and lubrication.
Oil injection temperatures for these units
should be 130°F or above depending on
ambient air temperature.
Air flow to/through the air end is controlled by
the intake valve. When there is a demand for
air, up to the rated capacity of the air end, the
intake valve will be open (air end fully loaded.)
When there is no demand for air the intake
valve will be closed (air end fully unloaded.)
CONTROL FUNCTION
MODULATING CONTROL
(Cub, Upper Range Modulation)
To obtain modulating control, a control
pressure regulator valve is used. The control
pressure regulator valve partially or fully
unloads the air end in direct proportion to air
demand.
As air demand is reduced (unit air received
pressure rises), the control pressure regulator
valve will gradually close the intake valve.
When the demand for air is less than the
rated capacity of the air end, the control
pressure regulator valve will hold the intake
valve partially closed causing the air end to
deliver air in direct proportion to demand.
When/if there is no demand for air, both the
unit and storage receiver pressures will rise to
the maximum operating pressure.
The control pressure regulator valve will, at
the maximum operating pressure, hold the
intake valve completely closed, fully
unloaded.
A plant system or additional storage receiver
may not be required for modulating control
units provided the unit is tanked mounted.
If air demand varies widely (short periods of
high demand with short periods of low or no
demand) a system storage receiver is
desirable and recommended to prevent too
frequent cycling of the controls. (Bed plate
mounted units only).
HIGH TEMPERATURE SHUT DOWN
SWITCH (Figure 9)
The high air temperature shut down switch is
located in the discharge cavity of the rear
bearing retainer on the air end.
This is a normally closed temperature
sensitive switch. The purpose of this switch is
to shut the unit down in the event the air
temperature at the air end discharge rises
above 230° ± 5°F.
CAUTION
THE CAUSE OF A SHUT DOWN DUE TO
HIGH AIR/OIL TEMPERATURE MUST BE
CORRECTED BEFORE RESTARTING THE
UNIT.
To restart a unit, allow the unit to cool to
automatically reset the high temperature shut
down switch.
SAFETY SHUTDOWN
CHECK HIGH AIR TEMPERATURE
There is a high discharge air temperature
shutdown function built into the control on
each compressor. It is factory pre-set at
230°. This function should be checked at
regular intervals for proper operation, once a
month is recommended.
PROCEDURE:
1. Block off the cooling air discharge.
2. The compressor discharge temperature
will rise at a rapid rate. Shutdown should
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